An aircraft landing gear assembly can include structural members coupled via a coupling or joint which includes one or more bearings. For example, members can be movably coupled via a pin joint. A pin joint will generally include a plurality of bearings, each being located between the pin and one of the structural members.
Aircraft landing gear assembly joints can be designed to withstand static pressure in excess of 400 MPa. Static pressure results from first and second structural members acting on the joint while the aircraft is on the ground; for example, the lugs of side stay links acting on a common pin joint during aircraft taxiing, where the pin joint is subjected to multi-directional loading.
Aircraft landing gear assembly joints can also be designed to withstand dynamic pressure of around 150 MPa due to relative movement between the structural members; for example, during articulation of the landing gear between deployed and stowed conditions.
It is common for aircraft landing gear assembly joints to be periodically greased in order to maintain a low friction coefficient at the bearing surface to control the amount of wear, and to flush out contaminants. Integral grease channels can be provided within one or more of the structural members to enable grease to be introduced to the bearing surface during maintenance operations.
However, the present inventors have identified that grease channels can lead to increased joint complexity. Grease channels can also result in stress raisers, defining regions of weakness in the pin joint. Moreover, a maintenance engineer could overlook a joint during maintenance, resulting in increased friction and wear. It is also possible that different types of grease could be introduced into a joint, resulting in loss of lubrication performance. Grease can also be displaced under sustained load, leading to areas starved of lubricant.
The present inventors have also identified that the mass of known landing gear assemblies can be reduced.